1. Field of the Invention
The present invention relates to an image qualification method, and particularly to methods for optical navigation sensor.
2. Description of the Related Art
An optical navigation sensor determines movements by comparing correlation of images captured at different times. Thus, quality of image affects movements determined by the optical navigation sensor. The quality of image results from noise, blurring out of focus, illumination, etc. The LED (light emission diode) in association with the optical navigation sensor is caused to constantly illuminate to prevent error in determining movements resulting from variation of illumination. When the optical navigation sensor is exposed to illumination from a fluorescent light driven by 60 Hz or 50 Hz AC power, however, there are periodical variations in illumination resulting in flickers in images captured by the optical navigation sensor and subsequent errors in determining movements.
The disadvantage of conventional image qualification is that several image frames are needed to calculate correlations therebetween to determine if the optical navigation is out of focus. Therefore, several buffers are required and time delay is unavoidable. There is a need to provide an image qualification for optical navigation sensor, which requires only one image frame.